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1.
Development ; 150(23)2023 12 01.
Artículo en Inglés | MEDLINE | ID: mdl-37902104

RESUMEN

In early embryos of the caenogastropod snail Ilyanassa obsoleta, cytoplasmic segregation of a polar lobe is required for establishment of the D quadrant founder cell, empowering its great-granddaughter macromere 3D to act as a single-celled organizer that induces ectodermal pattern along the secondary body axis of the embryo. We present evidence that polar lobe inheritance is not sufficient to specify 3D potential, but rather makes the D macromere lineage responsive to some intercellular signal(s) required for normal expression of 3D-specific phenotypes. Experimental removal of multiple micromeres resulted in loss of organizer-linked MAPK activation, complete and specific defects of organizer-dependent larval organs, and progressive cell cycle retardation, leading to equalization of the normally accelerated division schedule of 3D (relative to the third-order macromeres of the A, B and C quadrants). Ablation of the second-quartet micromere 2d greatly potentiated the effects of first micromere quartet ablation. Our findings link organizer activation in I. obsoleta to the putative ancestral spiralian mechanism in which a signal from micromeres leads to specification of 3D among four initially equivalent macromeres.


Asunto(s)
Organizadores Embrionarios , Transducción de Señal , Animales , División Celular , Embrión de Mamíferos , Embrión no Mamífero/metabolismo
2.
Development ; 150(23)2023 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-38032089

RESUMEN

In early embryos of the caenogastropod snail Ilyanassa obsoleta, cytoplasmic segregation of a polar lobe is required for establishment of the D quadrant founder cell, empowering its great-granddaughter macromere 3D to act as a single-celled organizer that induces ectodermal pattern along the secondary body axis of the embryo. We present evidence that polar lobe inheritance is not sufficient to specify 3D potential, but rather makes the D macromere lineage responsive to some intercellular signal(s) required for normal expression of 3D-specific phenotypes. Experimental removal of multiple micromeres resulted in loss of organizer-linked MAPK activation, complete and specific defects of organizer-dependent larval organs, and progressive cell cycle retardation, leading to equalization of the normally accelerated division schedule of 3D (relative to the third-order macromeres of the A, B and C quadrants). Ablation of the second-quartet micromere 2d greatly potentiated the effects of first micromere quartet ablation. Our findings link organizer activation in I. obsoleta to the putative ancestral spiralian mechanism in which a signal from micromeres leads to specification of 3D among four initially equivalent macromeres.


Asunto(s)
Organizadores Embrionarios , Transducción de Señal , Animales , División Celular , Embrión de Mamíferos , Embrión no Mamífero/metabolismo
3.
J Exp Zool B Mol Dev Evol ; 342(2): 101-105, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38291725

RESUMEN

Embryos of Ilyanassa obsoleta (from Massachusetts and Florida) and Phrontis vibex (from Florida) were exposed to temperatures from 33 to 37°C. In both species, very young embryos are especially sensitive to thermal stress. Brief early heat shock did not disturb spiral cleavage geometry but led to variable, typically severe defects in larval morphogenesis and tissue differentiation. In Ilyanassa but not P. vibex, early heat shock resulted in immediate slowing or arrest of interphase progression during early cleavage. This reversible arrest was correlated with improved prognosis for larval development and (in Massachusetts snails, at least) depended on parental acclimation to warm temperature (~25.5°C). Embryos from Massachusetts snails housed at lower temperature (16°C) exhibited cytokinesis failure when briefly incubated at 33°C during early cleavage, and tissue differentiation failure during incubation at 33°C begun at later stages. This preliminary study reveals a case in which stress-conditioned parents may endow embryos with protection against potentially lethal thermal stress during the most vulnerable stages of life.


Asunto(s)
Hipertermia Inducida , Caracoles , Animales , Morfogénesis , Temperatura , Aclimatación
4.
Curr Opin Genet Dev ; 39: 168-174, 2016 08.
Artículo en Inglés | MEDLINE | ID: mdl-27497839

RESUMEN

Ilyanassa obsoleta has been a model system for experimental embryology for over a century. Here we highlight new insight into early cell lineage specification in Ilyanassa. As in all molluscs and other spiralians, stereotyped cleavage patterns establish a homunculus of regional founder cells. Ongoing studies are beginning to dissect mechanisms of asymmetric cell division that specify these cells' fates. This is only part of the story: overlaid on intrinsic cell identities is a graded 'organizer' signal, and emerging evidence suggests wider roles for short-range intercellular signaling. Modern methods, combined with the intrinsic experimental advantages of Ilyanassa, offer attractive opportunities for studying basic developmental cell biology as well as its evolution over a wide range of phylogenetic scales.


Asunto(s)
Desarrollo Embrionario/genética , Filogenia , Caracoles/genética , Animales , Linaje de la Célula/genética , Transducción de Señal/genética , Caracoles/crecimiento & desarrollo
5.
Neuron ; 82(1): 167-80, 2014 Apr 02.
Artículo en Inglés | MEDLINE | ID: mdl-24698274

RESUMEN

Peptide neuromodulators are released from a unique organelle: the dense-core vesicle. Dense-core vesicles are generated at the trans-Golgi and then sort cargo during maturation before being secreted. To identify proteins that act in this pathway, we performed a genetic screen in Caenorhabditis elegans for mutants defective in dense-core vesicle function. We identified two conserved Rab2-binding proteins: RUND-1, a RUN domain protein, and CCCP-1, a coiled-coil protein. RUND-1 and CCCP-1 colocalize with RAB-2 at the Golgi, and rab-2, rund-1, and cccp-1 mutants have similar defects in sorting soluble and transmembrane dense-core vesicle cargos. RUND-1 also interacts with the Rab2 GAP protein TBC-8 and the BAR domain protein RIC-19, a RAB-2 effector. In summary, a pathway of conserved proteins controls the maturation of dense-core vesicles at the trans-Golgi network.


Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Mutación/genética , Vesículas Secretoras/metabolismo , Proteína de Unión al GTP rab2/metabolismo , Análisis de Varianza , Animales , Animales Modificados Genéticamente , Caenorhabditis elegans , Proteínas de Caenorhabditis elegans/genética , Mapeo Cromosómico , Clonación Molecular , Endosomas/metabolismo , Endosomas/ultraestructura , Aparato de Golgi/metabolismo , Aparato de Golgi/ultraestructura , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Microscopía Electrónica de Transmisión , Datos de Secuencia Molecular , Transporte de Proteínas , Vesículas Secretoras/genética , Vesículas Secretoras/ultraestructura , Proteína de Unión al GTP rab2/genética
6.
PLoS One ; 4(5): e5506, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19430530

RESUMEN

Cell lineage studies in mollusk embryos have documented numerous variations on the lophotrochozoan theme of spiral cleavage. In the experimentally tractable embryo of the mud snail Ilyanassa, cell lineage has previously been described only up to the 29-cell stage. Here I provide a chronology of cell divisions in Ilyanassa to the stage of 84 cells (about 16 hours after first cleavage at 23 degrees C), and show spatial arrangements of identified nuclei at stages ranging from 27 to 84 cells. During this period the spiral cleavage pattern gives way to a bilaterally symmetric, dorsoventrally polarized pattern of mitotic timing and geometry. At the same time, the mesentoblast cell 4d rapidly proliferates to form twelve cells lying deep to the dorsal ectoderm. The onset of epiboly coincides with a period of mitotic quiescence throughout the ectoderm. As in other gastropod embryos, cell cycle lengths vary widely and predictably according to cell identity, and many of the longest cell cycles occur in small daughters of highly asymmetric divisions. While Ilyanassa shares many features of embryonic cell lineage with two other caenogastropod genera, Crepidula and Bithynia, it is distinguished by a general tendency toward earlier and more pronounced diversification of cell division pattern along axes of later differential growth.


Asunto(s)
Linaje de la Célula , Embrión no Mamífero/embriología , Caracoles/embriología , Animales , Evolución Biológica , Tipificación del Cuerpo , Ciclo Celular , División Celular , Proliferación Celular , Embrión no Mamífero/citología , Microscopía Fluorescente/métodos , Modelos Biológicos , Morfogénesis , Caracoles/clasificación , Especificidad de la Especie , Factores de Tiempo
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